Thanks for all the feedback. I have learned the following:
1.- The light sensitivity threshold of any given film can be tweaked but not really pushed
2.- If making a photo under difficult light conditions is more important than the scriptures of Saint Ansel, film can be pushed
3.- Don´t go to the racetrack without a gun
Photos are made four inches behind the camera
Pushing is term that was used by news photographers and photojounislists to let the darkroom techs know how to develop the film. I would shoot TX at 800, put the film and my record (who, what where on which frames and the exposure,) in an envelope which was sent to a lab for processing. I do understand the "science of sensitomerty" and use of the term pushing is just short hand. The trade off of loss of shadow detail and blocking highlights was made to get prints in dismal conditions when the use of flash was impractical. With the evolution from B&W to color in the 1980s most news photographers started (returned as it was standard practice in the 30s, 40, and 50s) to use flash rather than pushing color film, and I guess that the same approach is still being used for the new digitial systems. I still push film (underexposed overdevelop or use a divided developer) to shoot indoors or shoot with a long lens in dim light outdoors without a tripod. Because I still use the term push doesn't make me the village idiot.
Paul, hardly the "village idiot" by any stretch of the imagination. I've been using BTZS numbers lately and I don't even know what n, n+1 or n-1 is any more. Since I've been using SBR numbers, the rest is meaningless. Thank goodness I don't know anything about sensitometry other than it must work.
With Efke 100, I've been a-pushin' and a-pullin' to beat the band. A rose by any other name....(sorry Eric). tim
If you do it correctly, you can take advantage of the "up to one stop" increase in real speed without the huge increase in contrast that usually accompanies extending development without changing other parameters.
What other parameters to change? Dilution -- using a weaker working solution will promote local exhaustion, resulting in shadows getting more development than highlights. Agitation -- less agitation tends to promote the location exhaustion that dilution makes possible. So, dilute your developer (and use more liquid if necessary to be sure there's enough to develop the film), agitate less, and develop a lot longer, and you'll get up to about one stop increase in speed.
I do it routinely with HC-110 on Tri-X, TMY, Fomapan 100, J&C Pro 100, and now even with a Caffenol derivative on Agfa Copex Rapid. No, I'm not claiming I get EI 800 with the shadows of 400 -- more like I get EI 400 with the shadows people derate to 250 or 200 to get, though I can do the 800 version just as readily if needed...
Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.